Na+ Preintercalated MoO3 Microrods for Aqueous Zinc/Sodium Batteries with Enhanced Performance.

Layered molybdenum trioxide (MoO3) is being investigated as a cathode material with high theoretical capacity and holds promise for aqueous secondary batteries. Unfortunately, the severe structural degradation of MoO3 and insufficient intrinsic properties hinder its practical application. Herein, a Na+ preintercalation strategy is reported as an effective method to construct cathodes with high performance for aqueous zinc/sodium batteries (AZSBs). Compared with pristine MoO3, the Na+ preintercalated Na0.25MoO3 cathode delivers a reversible capacity of 251.1 mAh g-1 at 1 A g-1, achieves a capacity retention of 79.2% after 500 cycles, and exhibits a high rate capability (121.5 mAh g-1 at 20 A g-1), which is superior to that in most of the previous reports. Through the experimental measurements and density functional theory (DFT) calculations, the preintercalation method could shorten the forbidden band gap and modulate the electronic structure and hence effectively inhibit the structural collapse of MoO3 microrods, induce reversible Na+ insertion, and enhance the discharge potential. This work is of significance for further research on molybdenum-based compounds as cathode materials for aqueous secondary batteries.